Compact feed system and method for comminuted cellulosic material

ABSTRACT

A feed system for a comminuted cellulosic material including: a chip bin having an upper chip inlet, an interior chamber oriented generally vertically and a lower discharge port; at least one liquor inlet to the chip bin to inject liquor in the chip bin, wherein the chip bin retains sufficient liquor and chips within the interior chamber to create a hydraulic pressure on the chips at the lower discharge port; a generally horizontally oriented chip conveyor or tube coupled to the lower discharge port to receive the chips and liquor from the bin under the hydraulic pressure, wherein the conveyor or tube includes liquor injectors which inject liquor into the chips and the conveyor or tube, and a high pressure transfer device coupled to a discharge of the conveyor or tube to receive the chips and liquor, whereby the hydraulic pressure of the chips and liquor at the discharge of the chip bin is sufficient to feed the chips and liquor to the high pressure transfer device.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/186,123, filed on Jun. 11, 2009, the entirety ofwhich is incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to feed systems to deliver comminutedcellulosic fibrous materials, such as wood chips, to a continuousdigester treatment vessel and, particularly, relates to feeding thesematerials to a high pressure transfer device that converts a lowpressure slurry of the material to a high pressure slurry of thematerial that is transported to the digester treatment vessel.

In the pulping of comminuted cellulosic fibrous material (genericallyreferred to herein as “wood chips” or just “chips”) in a continuousdigester, the wood chips are treated to remove entrapped air and toimpregnate the chips with cooking liquor while raising the pressure andtemperature of the material to, for example, 150 degrees Celsius (150°C.) and 10 bar gauge (g). Typically, the chips are steamed to purge airand increase the temperature of the chips, impregnated with heatedcooking liquor, pressurized and transported as a slurry to the digester.

A conventional chip feeder assembly typically includes a chip bin, a lowpressure feeder, a steaming vessel, a vertical chip tube and a highpressure feeder to purge air from, heat and pressurize the chips.Examples of conventional high pressure feeder assemblies are disclosedin U.S. Pat. No. 5,968,314, which shows a chip feeding system for adigester having a vertical chip bin, a horizontal chip steaming vessel,a vertical chip tube (also referred to as a chip chute), and a highpressure feeder.

Conventionally, the chips in the chip bin are relatively dry areslurried with liquor downstream of the chip bin. However, liquor hasbeen added to the chip bin to slurry the chips to facilitate transportof the chips from the chip bin to the steaming vessel and the verticalchip tube.

Steam has also been added to the chips in the chip bin or in a steamingvessel. The chips may also be steamed in a steaming vessel downstream ofthe chip bin. At the discharge of the steaming vessel or in chipconveyor, liquor has been added to the chips to slurry the chips tofacilitate transfer of the chips.

The slurry has been moved by mechanical conveyors, e.g., horizontaltubes with screws and augers, to the vertical chip tube. The screws andaugers in the mechanical conveyors are driven by motors that requireenergy. These moving mechanical components, e.g., screws and augers, arecostly in terms of acquisition costs and operating costs. There is along felt need to reduce acquisition costs, maintenance costs and energycosts in chip feed systems.

The hydraulic pressure of the slurry in the vertical chip tube assistsin feeding the chips to the high pressure transfer device. As the chipslurry enters the top of the vertical chip tube, the slurry fills thetube and applies a hydraulic pressure to the chips at the bottom of thetube. The chip tube has a height to ensure that the mass of the chipslurry held in the tube forms a sufficient hydraulic pressure at thebottom discharge end of the tube to feed the chips to the high pressuretransfer device, such as a high pressure feeder.

Without sufficient the hydraulic pressure, the suction applied by thehigh pressure feeder to the incoming chip slurry may form gas bubbles inthe slurry entering the feeder. Once gas becomes entrained in theslurry, the slurry becomes partially compressible and more difficult topressurize. Gas in the slurry can reduce the efficiency of the highpressure feeder. In some circumstances, gas caused by lack of hydraulicpressure can block the flow of the chip slurry into the high pressurefeeder.

Vertical chip tubes have conventionally provided the needed hydraulicpressure to a chip slurry. A vertical chip tube may be 15 feet to 30feet (5 meters to 10 meters) in height. The height of the chip tubesubstantially increases the overall height of the chip feed system andrequires the chip bin to be at a relatively high elevation above thechip tube. The supporting structures needed for the chip bin and otherelevated portions of the chip feed system may be substantial. Forexample, the chip bin may be at an elevation of 115 feet (35 meters).There is a long felt need to reduce the height of the chip feed systemto minimize the structure necessary for the system, and reduceconstruction and maintenance costs of chip feed systems.

BRIEF DESCRIPTION OF THE INVENTION

A chip feed system has been developed that floods a lower portion of achip bin with liquor to form a chip slurry in the bin. The slurry in thebin creates hydraulic pressure at the lower discharge of the bin. Thehydraulic pressure is sufficient to feed the chip slurry to a highpressure transfer device. Flooding the chip bin can render unnecessarythe chip tube.

A chip screw conveyor or chip tube arranged horizontally receives thechip slurry under the hydraulic pressure from the chip bin and feeds thechip slurry to a high pressure transfer device, such as a high pressurepump or high pressure feeder (HPF). Because the hydraulic pressure iscreated in the chip bin, a chip tube is unnecessary. The chip bin may bepositioned at a lower elevation than would be possible if a chip tubewere between the bin and the high pressure transfer device.

Flooding the chip bin with liquor creates a slurry of comminutedcellulosic fibrous material in the bin. The hydraulic pressure resultingfrom the liquor in the bin is sufficient to create the hydraulicpressure needed to feed a high pressure transfer device coupled to acontinuous digester. In some cases, the hydraulic pressure formed in thechip bin may eliminate the need for mechanical chip conveyance devicesthereby eliminating mechanical actions on the comminuted cellulosicmaterial and eliminating damage from mechanical action on the chipmaterial. Avoiding mechanical chip conveyors may reduce the capital andoperating costs of chip transport and improved the physical pulpproperties such as better burst strength, tensile strength and tearstrength.

A vertical chip tube is not needed because the flooded chip bin appliessufficient hydraulic pressure to feed the chips to a high pressuretransfer device. By doing away with a vertical chip tube, the chip feeddelivery may be shorter in height than conventional chip feed systemshaving vertical chip tubes. A shorter chip feed systems require fewerand smaller structural supports that would otherwise be needed toelevate the chip bin to a high elevation and support the chip tube. Forexample, the chip feed system may have a height of about 6 feet (20meters). In contrast, a conventional chip feed system with a horizontalchip tube for a similarly sized digester vessel may have a height of 115feet (35 meters).

Eliminating the chip tube by flooding the chip bin may reduce the heightof the chip feed system by, for example, 20 feet (7 m) to 55 feet (17m). This reduction in the height of the chip feed system providessubstantial savings in construction and maintenance costs by reducingthe amount of structural steel and other material necessary to providethe high elevation of the chip bin in conventional systems and makes thechip bin more easily accessed by lowering its elevation.

Further, the chip feed system with a flooded chip bin provides a highchip delivery capacity to feed a relatively large chip slurry flow rateto the high pressure feeder or other transport device. By eliminatingthe chip tube, restrictions on the rate of chip flow through the chiptube are eliminated. The rate of chip slurry flow may be determined bythe capacity of the chip bin which is typically a higher capacity thanthe flow capacity of conventional chip tubes.

In addition, a substantially horizontal chip tube may move the chips byhydraulically moving the chip slurry through and out of the tube.Hydraulic forces are applied by the injection of liquor or steam intothe tube. Nozzles for liquor or steam (or both) are arranged along thelength of the tube to inject jets of liquor or steam angled towards thedirection of chip flow through the tube. Further, jets of liquor orsteam at the outlet of the chip tube are optionally applied to force thechip slurry from the tube and into a conduit feeding the high pressurefeeder.

The horizontal chip tube may lack moving components such as screws andaugers. By reducing or eliminating a need for a screw or auger, thehorizontal chip tube has fewer mechanically moving components ascompared to horizontal chip tubes with rotating screws and augers.

A feed system is disclosed for a comminuted cellulosic materialcomprising: a chip bin including an upper chip inlet, an interior chipchamber oriented generally vertically and a lower discharge port; atleast one liquor inlet to the chip bin to inject liquor in the chipchamber, wherein the chip bin retains sufficient liquor and chips withinthe interior chamber to create a hydraulic pressure on the chips at thelower discharge port; a generally horizontally oriented chip conveyor ortube coupled to the lower discharge port to receive the chips and liquorfrom the bin under the hydraulic pressure, wherein the conveyor or tubeincludes liquor injectors which inject liquor into the chips in theconveyor or tube, and a high pressure transfer device coupled to adischarge of the conveyor or tube to receive the chips and liquor,whereby the hydraulic pressure of the chips and liquor at the dischargeof the chip bin is sufficient to feed the chips and liquor to the highpressure transfer device.

A method is disclosed to feed cellulosic fibrous material to a highpressure transfer device comprising: feeding the cellulosic fibrousmaterial to an upper inlet of a chip bin; adding liquor to the chip binto at least partially fill the chip bin with a slurry of the liquor andthe fibrous material; creating a hydraulic pressure in the slurry at alower discharge of the chip bin due to the liquor in the chip bin;discharging the slurry under the hydraulic pressure to a substantiallyhorizontal conveyor or tube; injecting liquor into the conveyor or tubeto move the slurry to an outlet of the conveyor or tube, and conveyingthe slurry under the hydraulic pressure from the outlet of the conveyoror tube to an inlet of the high pressure transfer device.

A chip tube comprising: a substantially horizontal tube having an inletadapted to attach to a discharge outlet of a chip bin and an outletadapted to be in fluid communication with a chip feeder; a chip slurrypassage within the tube extending from the inlet to the outlet; at leastone fluid injection nozzle attached to the tube and adapted to inject afluid into the chip tube, wherein the fluid injection nozzle is at angleto inject the fluid towards a first end of the tube proximate to theoutlet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a chip bin having a flooded lowerbin portion and a bottom outlet, wherein the bin is coupled to ahorizontal flooded twin-screw feeder discharging chips directly to ahigh pressure transfer device.

FIG. 2 is a schematic diagram showing a chip bin having a flooded lowerbin portion and a bottom outlet, wherein the bin is coupled to a floodedhorizontal chip tube feeder discharging chips directly to a highpressure transfer device.

FIG. 3 is a schematic diagram showing a chip bin having a flooded lowerbin portion and a bottom outlet, wherein the bin is coupled to a floodedhorizontal chip tube feeder discharging chips directly to a highpressure transfer device.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a chip feed system 10 having a chip bin 11 with a closedtop 12 with a conventional top chip inlet 14. The chip bin 11 is avertical vessel with a bottom discharge 15. The chip inlet 14 mayinclude a metering screw 16 and an air lock 18. The metering screwreceives chips via a conduit or conveyor from a chip supply 20. A vent22 at the top 12 of the chip bin allows steam and other vapors toexhaust from the chip bin to a steam or vapor recovery system 24.

The chip bin 11 may include an upper chamber 26 that has a circular orelliptical cross-section and a diameter of, for example, about 10 to 15feet (3 to 5 meters). A chip level sensor 25, e.g., a gamma sensor, maybe included in the upper chamber to monitor the level and, thus, theamount of chips in the bin. The height of the upper chamber may beone-half to two-thirds the entire height of the chip bin.

Chips from the top chip inlet 14 enter and settle in the upper chamber26. The chips in the upper chamber form a column of chips that movedownward through the chip bin towards a lower chamber 28 of the chipbin. A controller 38, e.g., computer, monitors the chip level sensor 25and may adjust the chip meter screw 16 to maintain a desired level ofchips in the bin.

The chips in the upper chamber 26 may remain relatively dry or besteamed by steam nozzles 30 arranged on the outer wall of the uppersection. A steam source 32, e.g., a low pressure steam source, providessteam to the steam nozzles 30 that may be arranged at one or moreelevations in the upper chamber of the chip bin. The steam provides heatenergy to heat the chips in the upper chamber and to start steaming thechips.

The lower chamber 28 of the chip bin has at an upper end the samecross-section as the lower end of the upper chamber 26. Chips flowdirectly from the upper chamber to the lower chamber. The lower chamber28 of the chip bin is entirely or at least partially flooded withliquor. Similarly, a portion of the upper chamber 26 may be flooded withliquor. Liquor injection nozzles 32 are arranged in the lower chamber ofthe chip bin at, for example, various elevations of the outer wall ofthe chip bin. At each elevation, an array of liquor nozzles 32 may bedistributed around the perimeter of the outer wall of the lower chamberof the chip bin. For example, there may be two elevations of arrays ofliquor nozzles 32. The liquor nozzles 32 may be oriented at an angle ofbetween 15 degrees to 85 degrees down from horizontal to inject liquordownward into the chip bin. The downward injection of liquor assists inmoving the chops down through the chambers of the chip bin.

A source of liquor 34, e.g., white, green or black liquor, is coupled toeach of the liquor nozzles 32 by conduits 35 and valves 36. The valvesmay be manually adjusted and thereafter remain in a set position toregulate the flow of liquor to the nozzle associated with each valve(s).Alternatively, the valves may be controlled by the computer controller38 that adjusts the valves to achieve a desired elevation of flooding inthe chip bin. A sensor(s) 39, e.g., a float, pressure or optical sensor,may be positioned in the lower chamber of and the upper chamber of thechip bin to monitor the liquor level in the bin.

The geometry, e.g., cross-sectional geometry, of the lower section 28 ofthe chip bin 11 has a substantially circular cross-section open top 40and a substantially rectangular cross-section open bottom discharge 15.The lower section 28 has opposite side non-vertical gradually taperingplanar side walls 42. The planar side walls 42 make an angle which maybe about 20 degrees to 30 degrees. These angles may be set dependingupon the particular material handled by the chip bin 11, such as theparticular species of wood chips commonly fed to the bin. The lowerchamber 28 provides a smooth geometric transition between the circularconfiguration of the upper chamber 26 and the substantially rectangularbottom discharge 15. Between the opposite planar side walls 42, areopposite curved side walls 44 connected the planar side walls. Theplanar side walls 42 may each be generally triangular in plan view.These planar sidewalls may be arranged vertically in a diamond shape asshown in FIG. 1.

The sidewalls 42, 44 of the lower section may be welded together and tothe upper section to provide a continuous fluid-tight chamber 28 for thechips and liquor in the chip bin. The chamber 28 is generally hollow topromote the uniform movement of chips and liquor down through the chipbin. The chambers 26, 28 in the chip bin and, especially, the lowerchamber 28, are shaped to promote a uniform downward movement of chipsthrough the bin across the entire cross-sectional area of the bin. Chipbins that promote a uniform downward flow of chips are disclosed in U.S.Pat. No. 5,617,975 (see col. 6, ln. 65 to col. 8, ln. 52), the entiretyof which is incorporated by reference. Further, liquor, chip and steampreferably does not escape from the chip bin except by way of the lowerchip slurry discharge 15 and the upper steam and vapor vent 22.

The chip bin is partially flooded with liquor to create a slurry ofchips and liquor within the chip bin. The slurry creates an elevatedhydraulic pressure at the bottom discharge 15 of the chip bin. Thehydraulic pressure is sufficient to force the chip slurry into a highpressure transfer device 46, e.g., a pump(s) or a high pressure feederwithout the formation of gases at the inlet of the device 46. The amountof necessary hydraulic pressure is dependent on the requirements of thehigh pressure transfer device and the components, e.g., screw conveyorin horizontal chip tube 48, between the bin discharge 15 and the highpressure transfer device 46. The hydraulic pressure created by flooding,or at least partially flooding, the chip bin renders a conventionalvertical chip tube an unnecessary component to the inlet of the highpressure transfer device 46.

The level, e.g., liquid level, of the slurry in the chip bin may be setto achieve the desired hydraulic pressure. For example, the level of theslurry in the chip bin may be at 15 feet (3 meters) or in a range of 10feet to 20 feet (3 meters to 7 meters) of elevation from the bottomdischarge 15 of the chip bin to the upper surface level of the liquor inthe chip bin.

The rate of liquor injected into the chip bin 11, the rate of chipsentering the bin and the rate at which the slurry of chips is dischargedfrom the bin determines the level of liquor in the chip bin. Generally,the liquor level in the chip bin should remain at a predetermined level.Liquor level sensors 39 may sense the liquor level in the chip bin.Based on signals from these sensors, the controller 38 may adjust thevalves 36 to regulate the flow of liquor through the nozzles 32 andadjust the rates of chips entering and being discharged form the bin toachieve a desired liquor level in the chip bin.

The amount or rate of liquor injected in the chip bin may be in excessof the capacity of the chips to adsorb the liquor during the period thatthe chips are in the bin. An amount or rate of liquor may be sufficientto generate free liquid in the chip bin. The free liquid is helpful tocreate a slurry that promotes the discharge flow of chips from the chipbin and move the slurry through the transport device, such as a conveyor48 or chip tube 62, 82 (FIGS. 2 and 3) without the need for amechanically acting device.

Liquor 34 for the chip bin may be extracted from the treatment vessel,such as from a top separator device. The amount of liquor needed forcooking or other treatment in the treatment vessel is generally lessthan the amount of liquor desirable for transporting the liquor as aslurry through the conveyor, chip tube, pumps, high pressure transferdevices and associated conduits (pipes). The liquor in excess of thatneeded for cooking or treatment may be extracted from the slurry as itenters the treatment vessel such as by using a top separator. The excessliquor may be used black liquor 34 to inject into the chip bin andthereby create a sufficient hydraulic pressure. In addition, whiteliquor 34 may be injected in the chip bin.

By way of example, the amount of white liquor introduced in the chip binmay be ten (10) percent to fifty (50) percent of the total amount ofwhite liquor introduced in the pulping system generally including thechip bin, chip feed system and treatment vessel(s). All or most of theremainder amount of white liquor is preferably introduced in thetreatment vessel(s). The white liquors introduced in the chip bin and inthe treatment vessel are used to process, e.g., cook, the chips in thetreatment vessel.

For chips formed of heavy, hard woods, the amount of white liquorintroduced in the chip bin may be between 10 to 25 percent of the totalamount white liquor introduced in the pulping system. For chips formedof softwoods, the amount of white liquor introduced in the chip bin maybe between 25 to 50 percent of the total amount of white liquorintroduced in the pulping system.

The liquor added to the chip bin may be an initial flood of highconcentration white liquor that soaks the chips in the bin. In oneexample, the wood chip is heavy hard woods that adsorb an amount ofliquor 1.2 times the dry weight of wood. Light softwood chip tend toadsorb two times as much liquor as the dry weight of the wood. Theamount of liquor, e.g., white liquor, added at the bottom of the chipbin may be at least 0.2 to 1.0 times the dry weight of the wood in thechip bin. For a chip bin having light, softwood chips, the amount ofwhite liquor added to the chip bin may be at least between 0.6 to 1.0times the dry weight of the chips in the bin. Nevertheless, the amountof liquor in the chip bin is preferably sufficient to create thehydraulic pressure needed to feed the chips into a high pressure feeder.

The white liquor may be added a temperature lower than the temperatureof the chips in the chip bin. The lower temperature of the white liquorreduces the risk of premature cooking of the wood chips before the chipsare in the treatment vessel. The chips in the chip bin may be heated to100 degrees Celsius due to the addition of steam 22 to the chip bin. Thewhite liquor may be added a temperatures below 90 degrees Celsius, suchas at ambient temperatures.

The chip slurry is discharged under hydraulic pressure from the bottomdischarge 15 of the chip bin. The bottom discharge is coupled to agenerally horizontal twin-screw conveyor 48 which includes a helicalscrew in a cylindrical housing. the conveyor 48 may be substantiallyhorizontal, such as at an incline of no more than ten degrees.

The chip slurry enters the screw conveyor 48 and is moved by helicalscrews to the outlet end 50 of the conveyor. The outlet end has a lowerliquor inlet 52 which injects liquor as the chip slurry is dischargedthrough the upper outlet 50 from the screw conveyor to a conduit 54. Theinjection of liquor to the outlet end 50 of the screw conveyor promotesthe discharge of chips into the conduit 54 and assists in avoiding chipsplugging and blocking the discharge 50 of the screw conveyor. Theinjection of liquor may also be used to adjust the ratio of liquor tochips in the slurry to a ratio suitable for the high pressure transferdevice.

Nozzles 56 may inject steam or liquor (or both) at the lower inlet 52 topromote the movement of chips out the conveyor. The nozzles 56 may beoriented to apply jets or liquor or steam in a partially upwarddirection at the chips to assist in moving the chips out of the screwconveyor. The vertical nozzle 56 may be installed by modifying aconventional horizontal chip tube that has an upper chip outlet 78.

The slurry of chips flow through the conduit 54 to the high pressuretransfer device(s) 46, such as a series or parallel array of one or morepumps or a high pressure feeder. The high pressure transfer device maybe at an elevation substantially the same as, e.g., within 15 to 25vertical feet (5 to 8 meters), of the elevation of the bottom dischargeport 15 of the chip bin. The chip slurry is pressurized in the highpressure transfer device to a pressure level suitable for a treatmentvessel 58, such as continuous digester vessel having a top separatorinlet to receive the chip slurry from the conduit 54.

FIG. 2 shows a chip feed system 60 having a flooded chip bin 11 (asshown in FIGS. 1 and 2) and a horizontal chip tube 62 at the bottomdischarge 15 of the bin. The chip tube 62 replaces the screw conveyor 48shown in FIG. 1. The chip bin 11 in the feed system 60 operates in thesame manner, and has the same components and geometry as the chip bin 10described in connection with FIG. 1. In addition, a rotating scraper mayor may not be in the bottom of the chip bin to assist in discharging thechip slurry into the chip tube. The rotating scraper is a component ofthe chip bin and not the chip tube.

The chip tube 62 relies on hydraulic action to move the chip slurrythrough the tube from the chip bin and to the high pressure transferdevice 46. The hydraulic action includes the injection of liquor 34 orsteam through nozzles 70 arranged along the casing of the chip tube. Byhydraulically moving the chip slurry from the bin to the high pressurefeeder, the chip tube avoids mechanical screw and auger devices found inconventional chip conveyors (such as shown in FIG. 1). Costefficiencies, e.g., acquisition costs, energy costs and maintenancecosts, may be achieved by eliminating the screw and auger movingcomponents of a conventional chip conveyor.

The chips are discharged from the bin into the upper inlet 64 of thehorizontal chip tube 62. The coupling 66 between the bottom discharge 15of the chip bin and the upper inlet of the 64 is shaped to promote thesmooth and uniform flow of chips into the chip tube. The coupling 66 mayhave a geometrical cross-sectional shape, such as a circular,elliptical, race track or figure eight.

One or more liquor injectors 68 at the axial end of the chip tubeinjects liquor 34 or steam into the chip tube 62 to form a flow throughthe tube that draws chips from the bin and into the tube. Multipleliquor or steam injectors 68 at the axial end and adjacent the coupling66 to the chip tube may be used to inject liquor or steam into the chiptube to move the chips from the bin and into the chip tube.

The rate of chip flow from the chip bin to the chip tube 62 may becontrolled by the amount of liquor or steam injected through injector(s)68. Similarly, liquor or steam may be injected along the length of thechip tube from nozzles 70 arranged in the sidewall of the chip tube.These nozzles 70 may be oriented to angle the flow of injected liquor ingenerally the same direction as the desired flow of the chips throughthe chip tube. These nozzles 70 move the chips through the chip tube andassist in controlling the rate of chip flow through the chip tube. Theliquor added from the nozzles 70 may also be used to dilute the chips inthe slurry to a chip to slurry ratio suitable for the high pressuretransfer device 46 downstream of the chip tube.

A vertically oriented nozzle 72 at the discharge end of the chip tubeinjects liquor or steam to propel the chips vertically upward from thechip tube and into the conduit 54.

Each of the injectors 68 and nozzles 70, 72 (which may structurally bethe same nozzle models) may have a corresponding valve 74 to control theflow of liquor or steam to the injector or nozzle. These valves 74 maybe set manually or controlled by the controller 38 based on flow sensor76 signals in the conduit 54 or at the high pressure transfer device 46.

The chip tube 62 may be a substantially cylindrical tube having an axisand a chip slurry center passage that is substantially fee ofobstructions. The casing of the chip tube has mounted thereon thenozzles 70, 72, that are positioned and angled to move the chip slurrythrough the center passage from the chip inlet to the chip outlet. Thenozzles may be mounted at an oblique angle, e.g., 10 degrees to 45degrees, on the tube casing. The angle of the nozzle orients the fluidstream form the nozzles into the center passage in a direction of chipflow through the passage. The nozzles inject the fluid along an axis ofthe tube and into a second end of the tube proximate to the inlet. Thenozzles may include an axially mounted nozzle proximate to an inlet endof the tube, an array of nozzles at a plurality of nozzle mountsarranged along the casing of the chip tube between the inlet and theoutlet, and nozzles adjacent the outlet of the chip tube.

FIG. 3 shows another chip feed system 80 having a flooded chip bin 11(as shown in FIGS. 1 and 2) and a horizontal chip tube 82 at the bottomdischarge 15 of the bin. The chip tube 82 is similar to the chip tube 62shown in FIG. 3, except that the chip tube 82 has an axial (either inplane or out of plane) chip slurry discharge port 84. The chip slurrydischarges from the chip tube to the conduit 54 in substantially thesame direction as the chip slurry flow through the chip tube. Becausethe chip slurry flow is not turned as it exits the chip tube, avertically oriented liquor nozzle (see FIG. 3 at 72) is not needed atthe outlet of the chip tube 84.

The conduit 54 transports the chip slurry to the high pressure transferdevice 46. Valves 86 in the conduit may control the flow and pressure ofthe chip slurry in the conduit. In addition, nozzles 88 with associatedvalves 74 may inject liquor or steam to assist in moving the slurrythrough the conduit 54 and to dilute the slurry. The valve 86 and valve74 for the nozzle(s) 88 may be manually set or controlled by thecontroller 38 to provide an desired chip slurry flow or pressure in theconduit 54. Further, the conduit 54 may be eliminated and the highpressure transport device, e.g., a pump, may be directly coupled to theoutlet 84 of the chip tube 82.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A feed system for a comminuted cellulosicmaterial comprising: a chip bin including an upper chip inlet, aninterior chamber oriented vertically and a lower discharge port, whereinthe chip bin includes an upper chamber having a continuously curvedcross section, and a lower chamber having a curvilinear cross sectionand an cross-sectional area decreasing in a downward direction; a chipmetering device configured to convey dry chips provided from a chipsupply to the upper chip inlet; liquor inlets to the chip bin positionedat multiple elevations on the lower chamber of the chip bin and adaptedto inject liquor in the lower chamber, wherein the chip bin retainssufficient liquor and chips within the lower chamber to create ahydraulic pressure on the chips at the lower discharge port; ahorizontally oriented chip transport device coupled to the lowerdischarge port to receive the chips and liquor from the bin under thehydraulic pressure, and a high pressure transfer device having an inletcoupled to a discharge of the chip transport device to receive the chipsand liquor directly from the chip transport device, wherein the inlet ofthe high pressure transfer device is at an elevation equal to or higherthan an elevation of the discharge of the chip transport device, andwherein the hydraulic pressure of the chips and liquor at the dischargeof the chip bin is sufficient to feed the chips and liquor to the highpressure transfer device, and the hydraulic pressure is equal to orhigher than a pressure of the chips and liquor at the inlet of the highpressure transfer device.
 2. The feed system of claim 1 wherein theliquor level in the chip bin is at least 15 feet above the lowerdischarge port of the chip bin, and the chip bin is flooded with liquorand chips between the liquor level and the lower discharge port.
 3. Thefeed system of claim 1 wherein the chip transport device is a horizontalchip tube with liquor injectors which inject liquor into the chips andliquor in the chip tube.
 4. The feed system of claim 1 wherein the chiptransport device includes a mechanical screw conveyor or auger conveyor.5. The feed system of claim 1 wherein the chip transport device is achip tube having liquor nozzles arranged to direct liquor into the chiptube to hydraulically move the chips through the chip tube to thedischarge of the chip transport device.
 6. The feed system of claim 1wherein the at least one liquor inlet to the chip bin is an array ofliquor nozzles arranged around a perimeter of the chip bin at aplurality of elevations on the chip bin.
 7. The feed system of claim 1wherein the at least one liquor inlet to the chip bin includes a liquornozzle oriented at an angle of between 15 degrees to 85 degrees downfrom horizontal to inject liquor downward into the chip bin.
 8. The feedsystem of claim 1 wherein the upper chamber of the chip bin has acircular or elliptical cross section and the lower chamber of the chipbin includes planar tapered opposing sidewalls.
 9. The feed system ofclaim 1 wherein the lower discharge port is at an elevation within 15feet of an elevation of the high pressure transfer device.
 10. A feedsystem for a comminuted cellulosic material comprising: a chip binincluding an upper chip inlet, an interior chamber oriented verticallyand a lower discharge port, wherein the chip bin includes an upperchamber having a continuously curved cross section, and a lower chamberhaving a curvilinear cross section and an cross-sectional areadecreasing in a downward direction; a chip metering device configured toconvey dry chips provided from a chip supply to the upper chip inlet; atleast one liquid liquor inlet to the chip bin adapted to inject liquidliquor in the chip bin, wherein the chip bin retains sufficient liquorand chips within the interior chamber to create a hydraulic pressure onthe chips at the lower discharge port; a liquid liquor level in the chipbin is at least 10 feet above the lower discharge port; a horizontallyoriented chip transport device coupled to the lower discharge port toreceive the chips and liquor from the bin under the hydraulic pressure,and a high pressure transfer device including an inlet coupled to adischarge of the chip transport device to receive the chips and liquor,wherein the inlet of the high pressure transfer device is at anelevation equal to or higher than an elevation of the discharge of thechip transport device, and wherein the hydraulic pressure of the chipsand liquor at the discharge of the chip bin is sufficient to feed thechips and liquor to the high pressure transfer device, and the hydraulicpressure at the discharge of the chip bin is equivalent to or higherthan a pressure of the chips and liquor at the inlet to the highpressure transfer device.
 11. The feed system of claim 10 the chiptransport device includes a chip tube having liquor nozzles arranged todirect liquor into the chip tube to hydraulically move the chips throughthe chip tube to the discharge of the chip transport device.
 12. Thefeed system of claim 10 wherein the lower discharge port is at anelevation within 15 feet of an elevation of the high pressure transferdevice.
 13. A feed system for a comminuted cellulosic materialcomprising: a chip bin including an upper chip inlet, an interiorchamber oriented vertically and a lower discharge port, wherein the chipbin includes an upper chamber having a continuously curved crosssection, and a lower chamber having a curvilinear cross section and ancross-sectional area decreasing in a downward direction; a chip meteringdevice configured to convey dry chips provided from a chip supply to theupper chip inlet; liquid liquor inlet arranged at different elevationson the lower chamber of the chip bin and the upper chamber is devoid ofliquor inlets, wherein the liquid liquor inlets are adapted to injectliquid liquor into the lower chamber of the chip bin, and wherein thechip bin retains sufficient liquor and chips within the interior chamberto create a hydraulic pressure on the chips at the lower discharge port;a chip tube having an inlet directly connected to the lower dischargeport to receive the chips and liquor from the bin under the hydraulicpressure, wherein the chip tube has a horizontal orientation, and a highpressure transfer device having an inlet connected to the discharge ofthe chip tube, such that chips and liquor flow directly from the chiptube to the high pressure transfer device; wherein the inlet to the highpressure transfer device is at the same elevation or higher than anelevation of the discharge of the chip tube, and wherein the hydraulicpressure of the chips and liquor at the discharge of the chip bin isequal to or higher than a pressure of the chips and liquor at the inletof the high pressure transfer device.
 14. The feed system of claim 13wherein the liquor level in the chip bin is at least 10 feet above thelower discharge port of the chip bin, and the chip bin is flooded withliquor and chips between the liquor level and the lower discharge port.15. The feed system of claim 13 wherein the chip tube includes liquorinjectors which inject liquor into the chips and liquor in the chiptransport device.
 16. The feed system of claim 13 wherein the chip tubeis substantially horizontal.
 17. The feed system of claim 13 wherein thechip tube includes a mechanical screw conveyor or auger conveyor. 18.The feed system of claim 13 further comprising liquor nozzles arrangedto direct liquor into the chip tube to hydraulically move the chipsthrough the chip tube to the high pressure transfer device.
 19. The feedsystem of claim 13 wherein the lower discharge port is at an elevationwithin 15 feet of an elevation of the high pressure transfer device.